Pressure gun



Dec. 22, I1942. i E w; McKNlGHT 2,305,976

PRESSURE GUN Filed oct. 23, 1940 Patented Dec. 22, 1942 UNITED STATS` TENT OFFICE 3 Claims.

Vduently coated with enamel, such as when used Yin the construction of steel automobile bodies, it

has been found desirable to roughen the surface of these sheets yto permit the paint o-r enamel to adhere t0 the surface. The finishing rolls between which the sheets are passed for the purpose of finishing the sheets are therefore provided with a rough surface bearing a resem- Yblance to the rough surface of ne sand paper.

The degree of roughness of the hard steel nn- `ishing rolls so used in providing rough surfaced steel sheets is determined by the degree of roughness desired in the steel sheets. At present such rolls are roughened by placing them in a chamber and subjecting the surfaces of the rolls to a bombardment of steel particles, the size of the steel particles selected being determined by the degree of roughness desired on the surfaces of the steel sheets and the hard steel` rolls, larger steel particles being selected to provide a greater degree of roughness.

In the preparation and use of these hard steel rolls, it frequently happens that they become marred to an extent which causes the roll to leave an impression on the steel sheet being rolled and therefore result in the sheet being rejected on inspection. Such marring can occur through a steel clip or shaving passing through the rolls with one of the sheets, this chip or shaving leaving an indentation in the surface of A the corresponding roll so that in subsequent use of this' roll a pimple will be reproduced 0n the sheet each time the roll rotates one revolution.

Heretofore when such a dimple or indentation occurred in one of the rolls it was necessary to mainder of the roll, and then replace the roll in the mill. To avoid this costly and time consuming procedure, numerous attempts have been made to grind the roll while in the mill, and t0 roughen the area of the bright spot produced by grinding while the roll is still maintained in the line of service. Prior to the present invention these efforts have not been successful. v

lt is the principal object of the present invention to provide a pressure gun for the bombardment of the bright spot produced on a hardened steel roll as a result of the grinding away of a damaged spot on the roll and which can be used to roughen such bright spots while the roll is still maintained in the line of service, thereby to relieve the necessity of removing the damaged roll for the purpose of restoring its surface to the necessary uniform, properly roughened condition.

Another object of the invention is to provide such a gun in which a uniform bombardment of the hard steel particles is obtained, the particles being drawn into an air stream from a reservoir and forcibly ejected against the brightl spot to be roughened.

Another object of the invention is to provide such a gun which is of simple and inexpensive construction and will stand up under conditions of severe and constant use without getting out of order or requiring repairs.

at its upper end to provide a valve housing 6,

to the end of which `a barrel is detachably secured. The grip 5 is provided with a central bore 8 and is provided at the lower end of this bore 8 with a fitting 9 which is adapted for attachment to a compressed air supply hose I0, the air passing up through the bore 8 to a horizontal enlargedV valve chamber I2 which leads to a reduced passageway I5. The shoulder I6 provided between the enlarged chamber I2 and the 'reduced passage I5 is formed to provide a seat for a conical valve head I8. This valve head is mounted, by means of a pin I9, to the inner end of a valve stem 20, the valve head I8 being free to rotate around the pin I9 to a limited degree in order to permit it to adapt itself to the valve seat I6. f

The valve stem 2l] extends rearward through a packing gland indicated generally at 2| and including an inner cylindrical follower member 22, packing 23 and a. threaded head 24 which is screwed into the rear threaded end of the enlarged valve chamber I2 so as to compress the packing 23 against the cylindrical follower 22. This follower 22 bears at its inner end against a helical compression spring 25, the front end of which bears a-gainst the valve head I8. It will therefore be seen that the packing Agland 2l is maintained under the pressure imposed upon the spring 25 and that this spring in Yturn tends to hold the valve head i9 in an axially centered and closed position.

The valve stem 28 is moved rearwardly to unseat the valve head IS by means of a control lever 28. This control lever comprisesside parts 29 which are extended upwardly to form a fork straddling the valve stem and interposed between the packing gland 2l and a washer 30 secured to the rearwardly projecting end of the valve stem t by means of a nut 3l and a lock nut 32. The lower ends of the side parts 29 of the control lever Z8 are connected by an integral grip 34 and the control lever is pivotally mounted adjacent its center on a horizontal pin 35 which is secured to a boss 36 formed integrally with the grip 5 and projecting rearwardly therefrom immediately under the valve housing 6.

It will therefore be seen that pressing the grip portion 34 of the control lever 28 forwardly against the grip 5 will serve to draw the valve stem 20 rearwardly against the resistance of the helical compression spring 25 and permit compressed air from. the supply hose Ill to pass upwardly through the lbore 8, chamber I2 and past the valve seat I6 into the reduced passage I5.

The forward end of the valve chamber 6 is externally threaded as indicated at 38 and is also formed to provide an enlarged bore 39 extending a short distance inwardly from its front end and joining the reduced passage I5. A barrel 4G is secured to the front end of the valve chamber 6, this barrel being provided for this purpose with an annular flange 4I adjacent its rear reduced end 42, this flange fitting against the front end face of the valve chamber 6 and its reduced rear end 42 fitting into the enlarged bore 39 at the front end of the valve chamber 6. The barrel 46 is held in this position by a threaded sleeve 43 which is screwed onto the external threads 33 at the front end of the kvalve chamber 6 and which has an annular internal shoulder 44 which bears against the forward face of the annular flange 4i of the barrel. At its .rear end the barrel is provided with a coaxial bore 45 of reduced diameter leading to a coaxial bore `46 of enlarged diameter at the front end of the barrel and through which latter enlarged bore 46 the compressed air and hard steel particles are ejected from the gun and against the bright spot of the hard steel roll which is being.

ticles. For this purpose it is necessary that these particles be supplied by gravity to the rear end of the enlarged bore 46 of the barrel immediately adjacent its small bore 45 since at this point a suction is created through the discharge of the small stream of air from the small bore 45 into the enlarged bore 46. I have further found that it is necessary that both the small bore 45 and the large bore 46 be each of uniform diameter throughout its length in order to provide proper feeding of the hard steel particles to the air stream and to provide a uniform pattern of the particles in the blast of air discharged from the gun.

The reservoir 50 is shown as being in the form -of a container having an open top closed by a.

removable cover 5I and having a conical bottom 52 leading to a reduced neck 53. The de-l pending reduced neck 53 discharges into a cen-v tral passage 54 leading downwardly into the rear *end of the enlarged bore 46 immediately adjabarrel and this neck is provided with a rounding y flange 56 which is formed to t the periphery of the barrel. Thislfiange extends rearwardly under the forward end of the sleeve 43 and at its front end this ange 56 is secured by a ring 5l to the barrel 48. In order to conveniently tighten the forward end of the ange 56 against the barrel and hold'it in a locked position, the ring 5l is provided on its rear side with a circular recess 58 which is eccentrically disposed with reference to the bore 59 of the ring. It will be seen that upon slipping the ring 51 over the barrel of the gun with the forward end of the ange 56 entering the eccentric recess 58 that the ring and reservoir can readily be locked in position by the simple expedient of turning the ring so that the eccentric recess 58 will wedge against the forwardly projecting end of the flange '56 and hold it in locked engagement with the barrel.

In operation the reservoir 56 is iilled with a quantity of hard steel particles of a size selected to produce the desired degree of roughness on the hard steel roll being redressed. Compressed air is also supplied to the gun through the supply line I0.

When a steel particle becomes embedded in the roughened roll through which the steel sheets are passed so as to leave an indentation in the roughened surface of the steel sheets and cause them to be rejected, the rolling mill is shut down Afor a sufficient length of time to permit the embedded particle to be located and to permit this particle to be ground out by means of a grinding stone. This grinding leaves a bright spot upon the roll and the gun forming the subject of the present invention is then brought into operation. The operator directs the barrel 46 of the gun against the bright spot and presses the grip piece 34 of the control lever 28 against the grip k5 so as tc draw the valve stem 2* rearwardly and unseat the valve head i8 froml its seat I6 against the resistance of the helical compression spring This permits compressed air to flow past the valve seat through the axial enlarged .bore I5 and reduced bore 45 into the enlarged main bore 46 of the barrel 4i). The discharge of the coinpressed air from the reduced bore 45 into the coaxial main enlarged bore i5 of the barrel creates a suction in the passage 54 which draws the steel particles downwardly so that these particles are drawn into the air stream by the suction eiTect created as well as by the force of gravity The particles so drawn out of the reservoir i] are discharged at high Velocity from the barrel de of the gun against the bright spot so that this bright spot is effectively roughened and its surface brought to the same condition as the rest of the peripheral surface of the roll. After the bright spot has been completely roughened to so conform to the rest of the roll surface, the gun is withdrawn, the roll `cleaned and the mill placed back in operation.

It will further be seen that the reservoir E!! can readily be removed by the simple expedient of rotating the ring 57 so as to bring its eccentric recess 58 to a position where the ange 56 of the reservoir is not wedged against the barrel iii?, the ring 51 being thereupon readily capable of being drawn forwardly so that the reservoir can be removed. It will further be seen that the gun is of extremely simple and inexpensive construction and will not get out of order or require repair or replacement under conditions of severe and constant use even considering the abrasive nature of the material which the gun is designed to bombard against the steel rolls. I claim as my invention:

1. A pressure gun for the application of heavy abrasive metal particles to roughen the surface of steel rolls, comprising a barrel having a large axial outlet bore of uniform diameter at its front end and having a small coaxial inlet bore of uniform diameter at its rear end communicating with said large bore, means for supplying air under pressure to said inlet bore of said barrel, and means for supplying by gravity heavy abrasive metal particles to one side of said large outlet bore immediately adjacent the discharge of said small inlet bore into said large outlet bore and in a vacuum zone created in said large outlet bore by the discharge of compressed air from said small inlet bore, comprising a vertical passage in said barrel leading from said large outlet bore to the exterior thereof, a reservoir having a discharge neck tting into said passage and adapted to be lled with a quantity of said heavy abrasive metal particles, a iiange projecting laterally from said neck and fitting along the top of said barrel and a collar rotatably mounted on said barrel and having a circular recess which is arranged eccentrically with reference to its bore, said eccentric recess being adapted to be fitted over said flange whereby upon turning said collar said ange is locked against said barrel.

2. A pressure gun for the application of heavy abrasive metal particles to roughen the surface of steel rolls, comprising a single metal body formed to provide a grip and a valve housing at the upper end of said grip, said valve housing being provided at its rear end with an enlarged horizontal bore and at its front end with a coaxial reduced bore communicating with the front end of said enlarged bore, the shoulder between said bores being formed to provide a valve seat, means for supplying compressed air to said enlarged bore, manually operable valve means arranged in said enlarged bore and cooperating with said valve seat to control the admission of compressed air to said small bore, said valve housing also being externally threaded at its front end and being provided at its front end with an enlarged circular recess arranged coaxially of said bores, a barrel projecting forwardly from said valve housing and having its rear end fitted in said recess and being provided adjacent its rear end with an annular ange engaging the front face of said valve housing around said recess, an internally threaded sleeve engaging the threaded front end of said valve body and having a shoulder engaging the forward face of said flange to hold said barrel in said recess, said barrrel also having a large outlet bore of uniform diameter at its front end arranged coaxially of said bores of said valve housing and having a small coaxial inlet bore of uniform diameter communicating with said large bore of said barrel and said reduced bore of said valve housing, and means for supplying heavy abrasive metal particles to one side of said large bore of said barrel immediately adjacent the discharge of said small inlet bore of said barrel into said large outlet bore of said barrel and in a vacuum zone created in said large outlet bore of said barrel by the discharge of compressed air from said small inlet bore of said barrel, comprising a vertical passage in said barrel leading from said enlarged bore of said barrel to the ex terior thereof, a reservoir having a discharge neck tting into said passage and adapted to be lled with a quantity of said heavy abrasive metal particles, a flange projecting transversely from said neck and tting along the top of said barrel and having one end tted between said sleeve and said barrel and a collar rotatably mounted on said barrel and having a circular recess which is arranged eccentrically with reference to its bore, said eccentric recess being adapted to be tted over the other end of said iiange whereby upon turning said collar said flange is locked against said barrel.

3. A pressure gun for the application of particles at high velocity against a surface to be treated, comprising a barrel having a bore which is open at one end, means for supplying air under pressure to the inner end of said bore and means for supplying by gravity particles to one side of said bore comprising a vertical passage in said barrel leading from said bore -to the exterior thereof, a reservoir having a discharge neck tting into said passage and adapted to be lled with a quantity of said particles, a flange projecting laterally from said neck and fitting around the top of said barrel, and a collar rotatably mounted on said barrel and having a circular recess which is arranged eccentrically with reference to its bore, said eccentric recess being adapted to be fitted over said flange whereby upon turning said collar said ange is locked against said barrel.

ELLIO'IT W. MCKNIGHT. 

